TITLE:   GCN CIRCULAR
NUMBER:  18797
SUBJECT: GRB 160101A: Swift/UVOT Detection
DATE:    16/01/01 15:52:34 GMT
FROM:    Mike Siegel at PSU/Swift MOC  <siegel@swift.psu.edu>

M. H. Siegel (PSU) and V. D'Elia (ASDC) report on behalf of the Swift/UVOT team:

The Swift/UVOT began tiled observations of the field of the MAXI-detected
burst GRB 160101A (Itoh et al. GCN Circ. 18793) 13.2 ks after the burst.  A
fading optical source consistent with position of the XRT source reported by
Izzo et al. (GCN Circ. 18795) is detected in the initial UVOT exposures in
the u filter.

The preliminary UVOT position is:
     RA  (J2000) =  14:38:36.12 = 219.65051 (deg.)
     Dec (J2000) = -13:48:55.4  = -13.81539 (deg.)
with an estimated uncertainty of 0.58 arc sec. (radius, 90% confidence).

Preliminary detections and 3-sigma upper limits using the UVOT 
photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for 
the early exposures are:

Filter     T_start(s)   T_stop(s)   Exp(s)       Mag
u           13195        13397       198     17.55+-0.10
u           19592        19652        59     18.32+-0.32

The magnitudes in the table are not corrected for the Galactic 
extinction due to the reddening of E(B-V) = 0.09 in the direction of the 
burst (Schlegel et al. 1998).